Vladimir Putin has put Russia's nuclear forces on alert as he is reportedly prepared to lose 50,000 troops to capture Ukraine.
The Russian tyrant is said to be "furious" that his forces have not been able to subdue the Ukrainians and blamed the West's sanctions for the move.
A burning Russian tank after it was hit by Ukrainian forces
Vladimir Putin put on a brave face despite Russian setbacks in Ukraine
Ukrainian soldiers inspecting a burnt out Russian military vehicle in Kharkiv
In an address on state TV, Putin claimed aggressive statements by NATO leaders and economic sanctions against Moscow have forced his hand.
He said he has now ordered his military command to put Russia's deterrence forces - a reference to units which include nuclear arms - on high alert.
He said "not only do Western countries take unfriendly measures" such as "illegal sanctions" but "top officials of leading NATO countries allow themselves to make aggressive statements with regards to our country".
“I order to move Russia’s deterrence forces to a special regime of duty,” Putin said.
Ahead of his invasion of Ukraine, Vladimir Putin warned Russia's "unparalleled" hypersonic missiles were ready for action.
And he chillingly warned Russia "today one of the most powerful nuclear powers".
"To anyone who would consider interfering from outside: If you do, you will face consequences greater than any you have faced in history."
The former chief of the Royal Navy, Lord West told The Sun one "miscalculation" could spark a war in Europe - which could spiral into a world war involving the use of nuclear weapons.
With Russian forces faltering, worrying new evidence has emerged about how much blood Putin is willing to shed in his quest to conquer Ukraine.
Intelligence chiefs have said he is willing for 50,000 of his troops to be sacrificed in the war, the Mirror reports.
The grim prediction comes as the Russian Ministry of Health is preparing for a massive medical emergency.
Officials are looking for doctors with a number of specialisms from across Russia to come forward, according to ITN.
Medical organisations should be be ready "to be promptly involved in activities aimed at saving lives and preserving the health of people in Russia", the ministry has urged.
In a speech marking the annual day of Special Operations Forces, Putin put on a brave face.
He said there should be "special gratitude to those heroically carrying out their military duty these days in the course of the special operation to provide assistance to the people's republics of Donbas".
The Russian leader was referring to the two Russian-speaking breakaway enclaves in Ukraine he has recognised as independent countries.
On more optimistic note, Ukrainian President Volodymyr Zelenskyy has agreed to peace talks with Russia.
Delegations from the two countries will meet on the border with Belarus, he said.
Shells rained down across Ukraine following the invasion in the early hours of Thursday - as the battle for the capital, Kyiv, stretched into a fourth day.
The city awoke to more air raid sirens after missile attacks that turned the sky orange during what Zelenskyy said was a "brutal" night.
And Ukrainian forces are battling the Russian invaders on the streets of Kharkiv and remain in "full control", local commanders say.
As his forces encounter stiff resistance from Ukrainians defending their homeland, the Kremlin strongman must be "furious" about the lack of progress, a former Nato defence chief has said.
"Putin is furious, he thought that the whole war would be easy and everything would be done in 1-4 days,” tweeted Riho Terras, who is also the former commander of the Estonian armed forces.
He said Ukrainian intelligence believes the Russians don't have a "tactical plan" to deal with an enemy that is fighting back.
“The Russians are in shock of the fierce resistance they have encountered,” Terras said.
The sky above Kyiv glowed orange as loud bangs were heard
An explosion was also seen in the city of Kharkiv after a gas pipeline was blown up
Smoke rises over Kyiv on Sunday morning
Earlier terrified civilians were urged to take cover in subways and basements as darkness fell.
Missiles kit Kyiv's main airport, Boryspil International and an oil depot was also blown up at at Vasylkiv, around 25m west of Kyiv.
Residents were warned the burning depot was emitting smoke and poisonous fumes and were told to keep their windows shut and to take cover.
Russian missiles also hit a nuclear waste disposal site on the outskirts of Kyiv, the Ukrainian State Nuclear Regulatory Inspectorate of Ukraine has confirmed.
People were asked not to turn lights on in their homes and keep well away from windows over fears of flying shards of glass.
There were widespread fears that the Russian army would step up its efforts to seize Kyiv this weekend, targeting commercial businesses in a bid to destroy Ukrainians' morale.
A city-wide curfew is being enforced in the capital while authorities hunt down "sabotage and reconnaissance groups," Kyiv's mayor said.
As midnight struck in the war-torn country, civilians and troops were urged to hunker down ahead of the "imminent" attack.
It marks the dawn of a fourth day of fighting as hero Ukranian troops and civilians scramble to beat off the Russian invaders.
It comes after a day of fighting during which Russian troops failed to capture the capital.
The official Ukraine death toll stands at 198, including three children.
And at least 17 of those were civilians, killed in a blast.
The Ukrainian Government has insisted the Russians are failing to advance with some 3,500 killed.
The UK Ministry of Defence tweeted in an intelligence update that Russian troops appear to be waning, suffering from "logistical challenges" and a strong, Ukrainian resistance.
The MoD confirmed that Russian troops had been injured and captured by Ukrainian forces.
A Ukrainian soldier stands in the charred remains of a battlefield